YAG sintered body and method for producing the same

Abstract

To provide a YAG sintered compact which can suppress particle dusting even when used in a plasma environment and has a high plasma resistance, and to provide a manufacturing method thereof.SOLUTION: A YAG sintered compact has an average particle diameter of 8 μm or more and 15 μm or less, and a ratio of the number of pores inside the particle to the number of all the pores within a cut face of 70% or more. By setting the particle diameter within a predetermined range, detachment of particles due to plasma corrosion hardly occurs. In addition, by setting a ratio of the number of pores inside the particle to the number of all the pores within the cut face to 70% or more, the plasma erosion from the pore hardly occurs. As a result, particle dusting is suppressed even when used in a plasma environment, which results in a YAG sintered compact having a high plasma resistance.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a YAG sintered body and a method for manufacturing the same.

Background Art

[0002] Conventionally, a Y3Al5O 12 (YAG) sintered body having good plasma resistance has been used as a member for semiconductor devices, particularly a member used in a plasma environment.

[0003] Patent Document 1 discloses a gas nozzle used in a plasma device, which includes a columnar main body made of a ceramic sintered body in which a through-hole through which gas flows is formed. At one end surface of the main body, an outlet of the gas in the through-hole is formed. The inner wall of the through-hole has a first region located near the outlet and a second region located inside the main body rather than the first region. The first region and the second region are composed of the fired surface of the ceramic sintered body, and the average crystal grain size in the first region is larger than the average crystal grain size in the second region.

[0004] Further, Patent Document 2 includes a substrate made of ceramics mainly composed of aluminum nitride and having a sample holding surface on its outer surface, and a conductor provided inside the substrate and facing the sample holding surface. Among the interior of the substrate, on the side of the sample holding surface rather than the conductor, the oxygen content in the ceramics is less in the region located more inward than in the region located outside the outer periphery of the conductor, and a sample holder is disclosed in which the particle size of the ceramics located near the conductor is larger than the particle size of the ceramics on the sample holding surface. Patent Document 2 states that it is preferable that the particle size of the ceramics in the vicinity of the electrostatic adsorption electrode in the low oxygen region is larger than the particle size of the ceramics on the sample holding surface, and that by reducing the particle size on the sample holding surface, the strength of the sample holding surface can be improved. Although cracks may occur on the sample holding surface, when the cracks on this surface are fine, the progress of the cracks stops at the grain boundaries, and the applied force is dispersed through the grain boundaries, and the length of the fine cracks is proportional to the size of the particle size of the ceramics.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] The ceramic sintered body is manufactured by a reaction sintering method in which a sintered body is produced by reaction during sintering for cost reduction, in addition to methods of sintering the raw material powder itself or the calcined powder together with a sintering aid or without a sintering aid. And the particle size of the sintered body is affected by its manufacturing method.

[0007] If the particle size of the surface layer of the sintered body is large, detachment of particles is likely to occur due to plasma corrosion, which has been the cause of particle dust generation that reduces the manufacturing yield of semiconductors and the like. Furthermore, the number of pores (the density of the sintered body) and the position where the pores are present similarly affected particle dust generation.

[0008] However, plasma resistance is a chemical resistance, and its properties vary greatly depending on the composition. Patent Document 1 describes ceramics as a general theory, and Patent Document 2 describes only AlN ceramics. However, regarding YAG ceramics, which are regarded as promising plasma-resistant materials, the relationship between their manufacturing method and plasma resistance was not clear from the above documents.

[0009] Therefore, even when used in a plasma environment, particle dust generation is suppressed, and a YAG sintered body with higher plasma resistance than before has been desired.

[0010] The present invention has been made in view of such circumstances, and an object thereof is to provide a YAG sintered body and a method for manufacturing the same, which can suppress particle dust generation even when used in a plasma environment and have high plasma resistance.

Means for Solving the Problems

[0011] (1) To achieve the above object, the YAG sintered body of the present invention is a YAG sintered body having an average particle size of 8 μm or more and 15 μm or less, and among the pores on the cut surface, the ratio of the number of pores present inside the grains is 70% or more.

[0012] In this way, when the average particle size is within a predetermined range, detachment of particles due to plasma corrosion is less likely to occur. Also, when the ratio of the number of pores present inside the grains among the pores on the cut surface is 70% or more, the plasma is less likely to erode from the pores. As a result, even when used in a plasma environment, particle dust generation is suppressed, and a YAG sintered body with high plasma resistance is obtained.

[0013] (2) Further, the YAG sintered body of the present invention is characterized in that the average particle size of the surface layer of the sintered body is smaller than the average particle size inside the sintered body on the cut surface.

[0014] By making the average particle size of the surface layer of the YAG sintered body smaller than that inside, even if particle detachment occurs from the surface, it can be easily discharged outside the process space, and the adhesion of particles to the substrate can be minimized.

[0015] (3) Further, the YAG sintered body of the present invention is characterized in that the number of pores per unit area of the surface layer of the sintered body is smaller than the number of pores per unit area inside the sintered body on the cut surface.

[0016] As a result, the surface structure has fewer pores than the internal structure and becomes a dense structure. Therefore, the generation of particles is suppressed, and the plasma resistance of the YAG sintered body is further increased.

[0017] (4) Further, the YAG sintered body of the present invention is characterized in that the average particle size of the surface layer of the sintered body and the average particle size inside the sintered body on the cut surface are substantially the same, the ratio of the number of pores present in the grains is 80% or more, and the relative density is 97% or more.

[0018] As a result, the surface and internal structures are uniform, and since most of the pores are present inside the grains, it is difficult for the surface to be damaged such as cracked by disturbances such as thermal load, it is stable, has high plasma resistance, and the generation of particles itself is suppressed.

[0019] (5) Further, the method for manufacturing a YAG sintered body of the present invention is a method for manufacturing a YAG sintered body, including a step of weighing a powder of an oxide of Y and a powder of an oxide of Al, a step of adding a binder to the weighed powders and mixing them, a step of granulating the mixed powders to form granulated powders, a step of molding the granulated powders to form a molded body, and a step of firing the molded body in an environment where a YAG pre-sintered body exists in a furnace.

[0020] Thus, by sintering in an environment where the YAG green compact exists together with the compact in the furnace, the reaction with the gas phase on the surface during reactive sintering can be adjusted, and the YAG sintered body described in the above (1) to (4) can be manufactured. Further, it can be manufactured at a lower cost as compared with the conventional manufacturing method in which YAG green powder is once synthesized, formed, and then fired.

Advantages of the Invention

[0021] According to the present invention, particle dust generation can be suppressed even when used in a plasma environment, and a YAG sintered body having high plasma resistance can be formed. Further, such a YAG sintered body can be manufactured.

Brief Description of the Drawings

[0022]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0023] Next, embodiments of the present invention will be described. In the configuration diagrams, the sizes of the respective components are conceptually shown and do not necessarily represent actual dimensional ratios.

[0024] [Configuration of YAG Sintered Body] (First Embodiment) The YAG sintered body of the present invention is composed of Y3Al5O 12 (YAG) crystals. Being composed of YAG crystals means that the phase of YAG is confirmed by the XRD (X-ray diffractometer) method and other phases are not substantially present, for example, it is 1% or less in a simple quantitative method such as the RIR method.

[0025] The YAG sintered body of the present invention has an average particle size of 8 μm or more and 15 μm or less. Thus, when the average particle size is within a predetermined range, the detachment of particles due to plasma corrosion is less likely to occur. The average particle size can be, for example, the average value of the values calculated by the intercept method by photographing in the field of view of an optical microscope with a magnification of 1000 times. The average particle size may be observed in three randomly selected fields so as to be the overall value of the YAG sintered body. Since the average particle size of the YAG sintered body of the present invention may vary depending on the depth from the surface, it is preferable that the overall average particle size is measured from the images at different depths from the surface and is the average value thereof. Further, when obtaining the average particle size of a predetermined region, it is measured on the surface satisfying the conditions.

[0026] For example, when obtaining the average particle size of the surface layer of the sintered body, an image photographed on the surface layer surface of the sintered body is used. The surface layer of the sintered body is defined as the range within 2.5 mm from the surface of the sintered body. Since the present invention may be characterized by the presence or absence of a difference between the surface layer and the internal structure of the YAG sintered body, it is preferable that the surface layer of the sintered body is as close as possible to the surface of the sintered body. Therefore, when the surface of the sintered body is a polished surface, the surface of the sintered body may be measured as the surface layer surface. Further, when the surface of the sintered body is a fired surface and the average particle size cannot be obtained, a surface obtained by polishing the surface of the sintered body by about 500 μm may be measured as the surface layer surface of the sintered body.

[0027] Further, for example, when obtaining the average particle size inside the sintered body, an image photographed in a field of view including a point inside the sintered body is used. The point inside the sintered body is defined as a point more than 5 mm away from the surface of the sintered body on the cross-sectional surface obtained by cutting the sintered body perpendicular to the surface.

[0028] In the YAG sintered body of the present invention, among the pores in the cross-sectional surface, the ratio of the number of pores existing in the grains is 70% or more, preferably 80% or more, and more preferably 85% or more. Thus, when the ratio of the number of pores existing in the grains among the pores in the cross-sectional surface is 70% or more, the plasma erosion from the pores is less likely to occur. As a result, even when used in a plasma environment, particle dust generation is suppressed, and a YAG sintered body with high plasma resistance is obtained.

[0029] The pores of the sintered body can be measured, for example, by photographing a cut surface or a polished surface with an optical microscope at a magnification of 1000 times, binarizing a randomly determined 100 μm × 100 μm field of view from the photographed image data using the free software "ImageJ" developed by the National Institutes of Health (NIH) in the United States, and identifying the pores. As for the measurement points, three fields of view may be randomly observed.

[0030] Also, the ratio of the pores present inside the grains is binarized using a different threshold value in the same field of view as the field of view in which the pores are identified, and the boundaries of the particles are determined. Then, the pores surrounded by the boundaries of the particles are defined as the pores present inside the grains (intragranular pores), and the pores at the triple points of the particles are defined as the pores present at the grain boundaries (grain boundary pores), and can be measured accordingly. Also in the measurement of pores, when obtaining the number of pores in a predetermined region or the ratio of the pores present inside the grains, the measurement is performed on a surface that satisfies the conditions.

[0031] Preferably, in the YAG sintered body according to this embodiment, the average particle size of the surface layer of the sintered body is smaller than the average particle size inside the sintered body on the cut surface. In this way, even if particle detachment occurs from the surface, it can be easily discharged outside the process space, and the adhesion of particles to the substrate can be minimized.

[0032] Preferably, in the YAG sintered body of the present invention, the number of pores per unit area of the surface layer of the sintered body is less than the number of pores per unit area inside the sintered body on the cut surface. As a result, the surface structure has fewer pores than the internal structure and becomes a dense structure. Therefore, the generation of particles is suppressed, and the plasma resistance of the YAG sintered body is further increased.

[0033] The YAG sintered body of the present invention preferably has a relative density of 95.0% or more, more preferably 97.0% or more, and even more preferably 98.0% or more. This is because the higher the relative density of the YAG sintered body, the higher the plasma resistance tends to be. The relative density of the YAG sintered body can be determined by the Archimedes method.

[0034] The total content of metals other than Y and Al in the YAG sintered body is preferably 100 ppm or less. By sufficiently reducing the total content of metals other than Y and Al in this way, the possibility that the YAG sintered body contains crystals or metals other than YAG can be sufficiently reduced. When the YAG sintered body contains crystals or metals other than YAG, the risk of corrosion by plasma starting from there increases. For example, when SiO2 is contained, the corrosion resistance to fluorine-based plasma decreases. Note that the YAG sintered body preferably has a lower content of elements other than Y, Al, and O, not limited to metals.

[0035] The contents of Y and Al in terms of oxides in the YAG sintered body, and the contents of metals other than Y and Al contained in the YAG sintered body can be measured by WDX (Wavelength Dispersive X-ray spectroscopy).

[0036] (Second Embodiment) The YAG sintered body according to this embodiment is the same as the YAG sintered body in the first embodiment, except that the preferable relationship between the average particle diameter of the surface layer of the sintered body and the average particle diameter inside the sintered body on the cut surface is different from that in the first embodiment. Therefore, the definitions of terms, preferable ranges, measurement methods, etc. other than the preferable relationship between the average particle diameter of the surface layer of the sintered body and the average particle diameter inside the sintered body on the cut surface in the first embodiment are all applicable to the YAG sintered body according to this embodiment.

[0037] Regarding the YAG sintered body according to this embodiment, it is preferable that the average particle diameter of the surface layer of the sintered body and the average particle diameter inside the sintered body on the cut surface are substantially the same. The fact that the average particle diameter of the surface layer of the sintered body and the average particle diameter inside the sintered body on the cut surface are substantially the same means that the difference between the average particle diameter of the surface layer of the sintered body and the average particle diameter inside the sintered body on the cut surface is within ±20% based on the average particle diameter inside.

[0038] As a result, since the structure of the surface and the inside is uniform and many of the pores exist inside the grains, it is difficult for the surface to be damaged such as cracked by disturbances such as thermal load, it is stable, and it has high plasma resistance and the generation of dust itself is suppressed.

[0039] The YAG sintered body according to the first embodiment of the present invention and the YAG sintered body according to the second embodiment are YAG sintered bodies with suppressed particle dust generation even when used in a plasma environment and high plasma resistance. In addition, in the members used in the actual products using the YAG sintered body of the present invention, the characteristics of the first embodiment and the characteristics of the second embodiment may be mixed. That is, even when a certain part of the member has the characteristics of the first embodiment and another part has the characteristics of the second embodiment, it can be said that it is a member using the YAG sintered body of the present invention. The reason is that the YAG sintered body according to the second embodiment is obtained by shaving the surface layer of the YAG sintered body according to the first embodiment.

[0040] [Usage example of YAG sintered body] Next, the usage example of the YAG sintered body of the present invention will be described. FIG. 1 is a schematic cross-sectional view showing a usage example of the YAG sintered body according to the embodiment of the present invention. The YAG sintered body of the present invention is used, for example, as a gas nozzle 10 used in a plasma device 100 such as a film forming device for forming a thin film on a substrate W such as a semiconductor wafer or a glass substrate, or an etching device for performing microfabrication on the substrate W in a semiconductor manufacturing process or a liquid crystal manufacturing process.

[0041] For example, in a film forming apparatus, a raw material gas containing a corrosive gas may be introduced into a reaction vessel 20 using a gas nozzle 10, and a thin film may be formed on a substrate W by a plasma CVD (Chemical Vapor Deposition) method in which this raw material gas is made into plasma. Further, in an etching apparatus, a halogen-based corrosive gas as a raw material gas may be introduced into a reaction vessel 20 using a gas nozzle 10, and this corrosive gas may be made into plasma to form an etching gas, thereby performing microfabrication on the substrate W.

[0042] The gas nozzle 10 has a gas supply port 11 to which a gas such as a corrosive gas is supplied from a gas supply unit (not shown), a gas discharge port 12 for discharging the gas into the reaction vessel 20, and a nozzle hole 13 that communicates the gas supply port 11 and the gas discharge port 12.

[0043] The YAG sintered body according to an embodiment of the present invention is a member having a portion exposed to a corrosive gas. Here, it is a member that constitutes at least a part of the portion of the gas nozzle 10 exposed to the corrosive gas, for example, the portion including the nozzle hole 13, and the portion exposed in the reaction vessel 20. However, the YAG sintered body may constitute the entire gas nozzle 10. Further, the YAG sintered body may be, for example, the container body 21 or the lid portion 22 that constitutes the reaction vessel 20, or a part thereof.

[0044] [Method for manufacturing YAG sintered body] Next, an example of a method for manufacturing the YAG sintered body of the present invention will be described. First, oxides of Y and Al are prepared as raw material powders for the ceramic sintered body. The oxide of Y is preferably Y2O3, and the oxide of Al is preferably Al2O3, but a substance that becomes YAG after sintering in an air atmosphere may also be used. The purity of each powder is preferably 99.9% or more, and more preferably 99.99% or more. Further, the average particle size of each powder is preferably 0.1 μm or more and 2.0 μm or less.

[0045] Next, each powder is weighed so that it has a predetermined composition ratio in terms of oxides in the YAG sintered body after sintering. The predetermined composition ratio is a composition in which Y is 37.5 mol% in terms of oxide (Y2O3) and Al is 62.5 mol% in terms of oxide (Al2O3) in the sintered body after firing. Although a deviation of about 1.0 mol% is allowed, it is preferably as close as possible to the predetermined composition ratio.

[0046] Next, the raw material powders are mixed. Each powder is put into a ball mill together with, for example, PVA as a solvent, and pulverized and mixed. As the ball mill, for example, alumina balls can be used. The mixing time can be, for example, 20 hours.

[0047] Next, the slurry is dried and granulated. Examples of the method for obtaining granulated powder from the slurry include a method of removing the solvent from the slurry by drying while simmering the slurry to obtain a powder and passing the obtained powder through a sieve. Also, a spray dryer can be used.

[0048] Next, the granulated powder is molded. The obtained granulated powder is molded by a press machine to obtain a molded body. As the molding method, press molding, CIP, hot press, HIP, etc. can be used. Also, in the case of press molding, the molding pressure can be, for example, 98 MPa.

[0049] Next, the molded body is fired in an environment where a YAG green compact exists in the furnace. The environment where a YAG green compact exists in the furnace means that, in addition to the molded body to be fired in the furnace, a green compact and a sintered body that already have the composition of YAG exist.

[0050] In this way, by sintering in an environment where a YAG green compact exists together with the molded body in the furnace, the reaction with the gas phase on the surface during reactive sintering can be adjusted, particle dust generation can be suppressed even when used in a plasma environment, and a YAG sintered body with high plasma resistance can be manufactured. Also, it can be manufactured at a lower cost compared to the conventional manufacturing method in which YAG green powder is once synthesized, then molded and fired.

[0051] The firing conditions may be the conditions of existing methods. For example, by firing the formed body at a temperature of 1700 °C for 1 hour or more in an air atmosphere, a sintered body can be obtained. Note that a step of pressurizing and densifying the fired body using HIP may be provided.

[0052] Further, a step of grinding or polishing the surface layer of the YAG sintered body may be provided so that the average particle diameter of the surface layer of the sintered body and the average particle diameter inside the sintered body on the cut surface are substantially the same.

[0053] By such a process, particle dust generation can be suppressed even when used in a plasma environment, and a YAG sintered body with high plasma resistance can be manufactured.

[0054] [Examples and Comparative Examples] (Method for preparing test pieces of Examples 1 and 2) Y2O3 raw material powder (purity 99.9%, average particle diameter 1 μm) and Al2O3 raw material powder (purity 99.99%, average particle diameter 0.5 μm) were weighed so that the mixing ratio of Y2O3 and Al2O3 was a mixing ratio of Y: 37.5 mol% and Al: 62.5 mol% in terms of molar ratio of atoms. Next, 2 wt% of a binder (PVA) was added to the weighed raw material powder, mixed, and granulated. Then, uniaxial press molding was performed. And the formed body was put into an alumina sleeve and fired at 1700 °C for 10 hours in an air atmosphere furnace to prepare test pieces. In Example 1, a YAG pre-sintered body was put into the sleeve in addition to the formed body. In Example 2, a YAG pre-sintered body was put into the sleeve in addition to the formed body, but the amount was set to about half of the amount in Example 1.

[0055] (Method for preparing test piece of Comparative Example 1) Y2O3 raw material powder (purity 99.9%, average particle size 1 μm) and Al2O3 raw material powder (purity 99.99%, average particle size 0.5 μm) were weighed so that the mixing ratio of Y2O3 and Al2O3 was Y: 37.5 mol% and Al: 62.5 mol% in terms of molar ratio of atoms. Next, 2 wt% of a binder (PVA) was added to the weighed raw material powder, mixed, and granulated. The granulated powder was fired in an air atmosphere furnace at 1700 °C for 10 hours to prepare YAG calcined powder.

[0056] This was pulverized by a ball mill to prepare YAG raw material powder with an average particle size of 3 μm. 2 wt% of a binder (PVA) was added to the prepared YAG raw material powder, mixed, and granulated. Then, uniaxial press molding was performed. And the molded body was put into an alumina sleeve, and fired in an air atmosphere furnace at 1700 °C for 10 hours to prepare test pieces.

[0057] (Evaluation method) The average particle size, number of pores, relative density, and plasma resistance of each test piece were measured and evaluated by the following tests. The size of each test piece was □30 mm × 15 mm. Figure 2 is a table showing the results of each test of the examples and comparative examples.

[0058] (Average particle size) The surface layer of the sintered body of each test piece, the inside of the sintered body on the cut surface, and the structure at a predetermined position on the cut surface were photographed in the field of view of an optical microscope at 1000 times magnification, and the average value of the values calculated by the intercept method was taken as the average particle size of each region or the whole. For the surface layer of the sintered body, three random locations on the surface obtained by polishing the fired surface by 500 μm were photographed. For the inside of the sintered body on the cut surface, points more than 5 mm away from the surfaces of three different cut surfaces cut perpendicular to the surface were randomly selected respectively, and photographed in the field of view including that point. For the predetermined position on the cut surface, points directly below the surface of three cut surfaces cut perpendicular to the surface, the center of the cut surface, and the midpoint between the center of the cut surface and the surface were selected, and photographed in the field of view including each point.

[0059] (Number of pores) The surface layer of the sintered body of each test piece and the internal structure of the sintered body on the cut surface were photographed respectively in the field of view of an optical microscope with a magnification of 1000 times. A field of view of □100 μm (a square of 100 μm × 100 μm) was randomly photographed at 3 locations, and the average value of the number of pores was taken as the number of pores. For the surface layer of the sintered body, the surface obtained by polishing the sintered surface by 500 μm was randomly photographed at 3 locations. For the inside of the sintered body on the cut surface, points more than 5 mm away from the surfaces of 3 different cut surfaces cut perpendicularly to the surface were randomly selected respectively, and photographed in the field of view including that point. The values shown in the table of Figure 2 are the values obtained by rounding the average value.

[0060] (Relative density) The bulk density of the sintered body was measured by the Archimedes method, and the relative density was calculated from the theoretical density. Test pieces with a relative density of 95% or more are dense as sintered bodies. In such a dense case, they can be suitably used as members for large semiconductor manufacturing equipment.

[0061] (Plasma resistance) One side of the test piece was mirror-polished and a part of it was masked with a polyimide tape. Then, the test piece was placed in a parallel plate type RIE etching apparatus in a vacuum chamber and exposed to CF4 + 20% O2 plasma for 10 hours, and the corrosion depth was measured. Those with a corrosion depth of 1 μm or less were rated as good (〇), and those larger than that were rated as bad (×).

[0062] (Evaluation results) For Examples 1 and 2, the average particle size of the surface layer of the sintered body was smaller than the average particle size of the inside of the sintered body. In contrast, for Comparative Example 1, the average particle size of the surface layer of the sintered body was slightly larger than the average particle size of the inside of the sintered body.

[0063] In addition, for the number of pores in Examples 1 and 2, the number of pores on the surface layer of the sintered body was less than the number of pores inside the sintered body. In contrast, for the number of pores in Comparative Example 1, the number of pores on the surface layer of the sintered body was slightly more than the number of pores inside the sintered body. Also, the ratio of the number of intragranular pores to the total number of all pores (the sum of the number of pores on the surface layer and the number of pores inside) in Examples 1 and 2 was generally high, and was 75% or more in any of the examples. FIGS. 3(a) and (b) are optical micrographs of the surface layer and the inside of the sintered body of Example 1, respectively.

[0064] Also, as shown in FIGS. 3(a) and (b), most of the pores inside the sintered bodies of Examples 1 and 2 were intragranular pores, and grain boundary pores were observed more as approaching the surface layer. Due to such characteristics, when the surface layer is polished to a certain extent, the grain boundary pores decrease, so it is considered that the plasma resistance is further improved.

[0065] In contrast, in Comparative Example 1, the ratio of intragranular pores was small, and most were grain boundary pores. Therefore, when comparing at the same relative density, it is considered that the YAG sintered body of the example has higher plasma resistance than the YAG sintered body of the comparative example.

[0066] These are presumably because in any of the examples, the grain boundaries became more wettable due to the reaction between Al2O3 and Y2O3, making it difficult for pores to form at the grain boundaries. In contrast, it is considered that in the comparative example, sintering is by volume diffusion of YAG particles, and pores at the triple points between particles are likely to remain.

[0067] The relative density was 97% or more in Examples 1 and 2, and they were dense. Also, the evaluation of plasma resistance was in a good range for both Examples 1 and 2.

[0068] (Example 3) The sintered body obtained by machining the surface layer of the sintered body produced under the same conditions as in Example 1 by grinding and polishing to a depth of 500 μm was used as the sintered body of Example 3. This is because the region with a smaller particle size in Example 1 was approximately 500 μm from the surface. The average particle size of the new surface was 11.3 μm, and the average particle size inside the sintered body at the cut surface was 12.8 μm. That is, it can be said that the average particle size of the surface layer of the sintered body of Example 3 and the average particle size inside the sintered body at the cut surface are substantially the same.

[0069] Also, the number of pores per unit area on the surface layer of the sintered body was 42, and the number of pores per unit area inside the sintered body at the cut surface was 40, with almost no difference. Thus, it was found that the YAG sintered body obtained by removing the surface layer of the sintered body by a predetermined thickness was a sintered body with extremely homogeneous particle size and pore distribution as a whole. Also, the plasma resistance of Example 3 was good.

[0070] Note that the thickness of the range with significantly different average particle sizes can be adjusted according to the manufacturing conditions. In Example 1, it was approximately 500 μm, while in Example 2, it was approximately 2.5 mm.

[0071] Based on the above results, it was confirmed that the YAG sintered body of the present invention suppresses particle dust generation even when used in a plasma environment and has high plasma resistance. Also, it was confirmed that the manufacturing method of the YAG sintered body of the present invention can produce such a YAG sintered body.

[0072] Note that the present invention is not limited to the above-described embodiments and can be appropriately modified without departing from the spirit of the invention.

Explanation of Reference Numerals

[0073] 10 Gas nozzle 11 Gas supply port 12 Gas discharge port 13 Nozzle hole 20 Reaction vessel 21 Vessel body 22 Lid part 100 Plasma device W substrate

Claims

1. A YAG sintered body, characterized in that: The average particle size of the surface layer of the YAG sintered body, the average particle size inside the YAG sintered body on the cut surface, and the average value of the average particle sizes at predetermined positions on the cut surface are 8 μm or more and 15 μm or less; The average particle size of the surface layer of the YAG sintered body is the average value of the particle size values calculated by the intercept method using the images taken by randomly selecting the structures of three regions randomly selected from the surface of the sintered skin surface of the YAG sintered body polished by 500 μm in a field of view of a 1000-fold optical microscope; The average particle size inside the YAG sintered body on the cut surface is the average value of the particle size values calculated by the intercept method using the images taken by randomly selecting points more than 5 mm away from the surface on three different cut surfaces cut perpendicular to the surface of the YAG sintered body, and photographing the structures of the regions including the points more than 5 mm away from the surface in a field of view of a 1000-fold optical microscope; The average particle size at a predetermined position on the cut surface is the average value of the particle size values calculated by the intercept method using the images taken by selecting the points directly below the surface of the three cut surfaces, the center of the cut surface, and the midpoint between the center of the cut surface and the surface, and photographing the structures of the regions including each point in a field of view of a 1000-fold optical microscope; Among the pores on the cut surface, the ratio of the number of pores existing inside the grains is 70% or more; The number of the pores is the average value of the number of pores included in a square region with a side length of 100 μm randomly selected at three locations by photographing the structure in a field of view of a 1000-fold optical microscope. A YAG sintered body characterized by the above.

2. The YAG sintered body according to claim 1, characterized in that the average particle size of the surface layer of the YAG sintered body is smaller than the average particle size inside the YAG sintered body on the cut surface.

3. The number of pores per unit area in three regions randomly selected from the surface of the YAG sintered body polished by 500 μm is less than the number of pores per unit area in the regions including points more than 5 mm away from the surface randomly selected from three different cut surfaces cut perpendicular to the surface of the YAG sintered body. The YAG sintered body according to claim 1 or claim 2.

4. The average particle diameter of the surface layer of the YAG sintered body and the average particle diameter inside the YAG sintered body on the cut surface are substantially the same, the ratio of the number of pores present in the grains is 80% or more, The YAG sintered body according to claim 1, characterized in that the relative density is 97% or more.

Images