Alumina sintered body parts

Abstract

To provide an alumina sintered compact member having low dielectric loss, excellent corrosion resistance, and reduced particle generation; an alumina sintered compact member capable of forming a uniform protective film on a surface thereof; and an alumina sintered compact member on which the uniform protective film is formed on the surface thereof.SOLUTION: An alumina sintered compact member of the present invention comprises an alumina sintered compact containing: at least 99.5% wt.% of aluminum oxide; 100 ppm or more but 1,000 ppm or less of Mg; 25 ppm or more but 100 ppm or less of Na; and 100 ppm or more but 1,000 ppm or less of Si, wherein the alumina sintered compact has a density of at least 3.97 g / cm3. An average particle diameter of alumina particles on any one surface of the alumina sintered compact in a (500×500 μm) square area is 2 μm or more but 6 μm or less; an average aspect ratio of the alumina particles is 0.5 or more but 1 or less; an arithmetic average height Sa in the square area is 0.2 μm or less; and an aspect ratio Str of the surface quality is 0.05 or more but less than 1.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an alumina sintered body member, and more particularly to an alumina sintered body member suitable as a material for components used in, for example, semiconductor manufacturing equipment. [Background technology]

[0002] Alumina sintered members are used as components of various semiconductor manufacturing devices, for example, devices that generate high frequency plasma, such as etchers. However, when an alumina sintered body member is exposed to high-frequency plasma in such an apparatus for generating high-frequency plasma, particles are generated, which poses a problem of reducing the yield of silicon wafers to be processed.

[0003] As one of the solutions to this problem, an alumina sintered body member having various protective films formed on the surface thereof is known. Conventionally, a thermal spray coating has been used as a protective coating formed on an alumina sintered body. For example, Patent Document 1 shows that by setting the average pore diameter on the surface of the alumina sintered body to 5 μm or less or the roughness Ra to less than 0.1 μm, the thermal spray coating can be formed uniformly and the surface condition of the thermal spray coating can be improved.

[0004] However, even if the surface texture is defined by the surface roughness Ra, ie, the line roughness, as in Patent Document 1, it is not possible to know the texture of the entire substrate surface in detail. Therefore, it has been proposed to further evaluate the surface quality by the surface roughness extended to the surface, and to specify the surface of the substrate by the arithmetic mean height Sa, as shown in Patent Document 2. That is, Patent Document 2 discloses a method for manufacturing a thermally sprayed member, which includes the steps of preparing spray particles having a median diameter D50 of 0.1 μm or more and 6 μm or less, preparing a substrate having an arithmetic mean surface height Sa [μm] that satisfies 0.04 × D50≦Sa≦1.4 × D50, and spraying the spray particles onto the surface of the substrate to form a thermally sprayed film on the surface of the substrate.

[0005] According to the invention disclosed in Patent Document 2, the median diameter D50 of the spray particles is small, at 0.1 μm or more and 6 μm or less, so that gaps are less likely to form between the spray particles and the substrate when the molten spray particles collide with and adhere to the surface of the substrate during thermal spraying, thereby improving the adhesion strength between the substrate and the sprayed coating.

[0006] Furthermore, for example, it is desirable that components used in semiconductor manufacturing equipment have low dielectric loss, and the value of tan δ, which is used as an index of dielectric loss, is sometimes evaluated by specifying the target frequency range. For example, Patent Document 3 describes a sintered body containing Al2O3 as the main component and 0.5 wt% or more of Y2O3, in which Y2O3 or a compound of Al2O3 and Y2O3 exists at the grain boundaries of the Al2O3 crystal phase, and the dielectric loss (tanδ) at 7 to 9 GHz is 1.0 × 10 -4 The following low dielectric loss materials are disclosed: [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2020-50536 [Patent Document 2] Japanese Patent Application Publication No. 2019-127598 [Patent Document 3] Japanese Patent Application Publication No. 8-325054 Summary of the Invention [Problem to be solved by the invention]

[0008] Incidentally, for example, it is preferable that alumina sintered bodies used in semiconductor manufacturing equipment have low dielectric loss. However, when 0.5 wt % or more of Y2O3 is added to alumina as disclosed in Patent Document 3 in order to obtain an alumina sintered body with low dielectric loss, it becomes difficult to uniformly distribute particles, including grain boundaries, on the surface of the sintered body, which results in an increase in surface irregularities. Therefore, the invention described in Patent Document 3 has a large uneven surface, and it is difficult to say that it is adequate to form a protective film on the surface in a good condition.

[0009] Furthermore, the invention described in Patent Document 2 uses spray particles with a median diameter D50 of 0.1 μm or more and 6 μm or less, and uses a substrate with an arithmetic mean height Sa that has a specific relationship with the median diameter D, but is not compatible with protective films formed by methods other than thermal spraying. Furthermore, the invention described in Patent Document 2 specifies the surface texture of the substrate using the arithmetic mean height Sa, but does not specify the surface texture appropriately for forming a protective film.

[0010] Furthermore, since pores in the sprayed film cause particles to be generated during the etching process, the introduction of dense film formation methods such as ion plating has been promoted in recent years. However, the surface properties of Patent Document 2 do not indicate suitable surface properties of a substrate that can be applied to a dense film formation method such as an ion plating method.

[0011] As described above, none of Patent Documents 1 to 3 has yet fully grasped the surface properties of a high-purity, low-dielectric-loss alumina sintered body that enable better formation of a protective film.

[0012] Therefore, the inventors of the present invention have intensively studied an alumina sintered body member suitable for forming a protective film, assuming that the alumina sintered body member is an alumina sintered body with low dielectric loss and that the alumina of the base material is of high purity, since if the base material of the alumina sintered body contains a large amount of elements other than alumina, these elements will segregate at the grain boundaries of the alumina and cause localized etching by plasma to proceed. As a result, they have completed the present invention.

[0013] The present invention has been made in view of the above circumstances, and has an object to provide an alumina sintered body member that has low dielectric loss, excellent corrosion resistance, and suppresses particle generation. Another object of the present invention is to provide an alumina sintered body member capable of forming a uniform protective film on the surface of an alumina sintered body (substrate), and an alumina sintered body member on which a uniform protective film has been formed on the surface of an alumina sintered body (substrate). [Means for solving the problem]

[0014] In order to solve the above problems, the alumina sintered body member according to the present invention contains at least 99.5 wt% aluminum oxide, 100 ppm to 1000 ppm of Mg, 25 ppm to 100 ppm of Na, and 100 ppm to 1000 ppm of Si, and has a density of at least 3.97 g / cm 3 The alumina sintered body is characterized in that the average particle size of the alumina particles in a square area (500 × 500 μm) on any one surface of the alumina sintered body is 2 μm or more and 6 μm or less, the average aspect ratio of the alumina particles is 0.5 or more and 1 or less, the arithmetic mean height Sa in the square area is 0.2 μm or less, and the aspect ratio Str of the surface texture is 0.05 or more and less than 1.

[0015] With this configuration, it is possible to obtain an alumina sintered body member that has low dielectric loss, excellent corrosion resistance, suppressed particle generation, and suppressed peeling of surface particles. Furthermore, since the surface of the alumina sintered body member has small irregularities, when a film is formed on the surface of the alumina sintered body (substrate), a uniform film can be formed. In addition, the alumina sintered body member according to the present invention has a dielectric loss (tan δ) of 1×10 -5 More than 1×10 -4 The following is the result.

[0016] Here, it is desirable that a protective film of ceramics containing yttrium is further formed on the surface of the alumina sintered body member, and that the protective film has a thickness of 1 μm or more and 20 μm or less, a porosity of 0.2% or less, an arithmetic mean height Sa of 0.2 μm or less, and an aspect ratio Str of the surface texture of 0.05 or more and less than 1.

[0017] In this way, when the protective film is made of ceramic containing yttrium, it is possible to further improve corrosion resistance against plasma. Furthermore, the surface properties of the protective film on the alumina sintered body member are substantially equivalent to the surface properties (Sa, Str) of the alumina sintered body serving as the base material. This reduces peeling on the surface of the protective film, and the alumina sintered body member on which the protective film is formed also has excellent low dielectric loss characteristics. In addition, in the alumina sintered body member on which the protective film according to the present invention is formed, the dielectric loss (tan δ) at 3 to 7 GHz is 1×10 -5 More than 1×10 -4 The following is the result. [Effects of the Invention]

[0018] According to the present invention, it is possible to obtain an alumina sintered body member having low dielectric loss, excellent corrosion resistance, and suppressed particle generation. Also, it is possible to obtain an alumina sintered body member in which a uniform protective film can be formed on the surface of the alumina sintered body (substrate), and an alumina sintered body member in which a uniform protective film is formed on the surface of the alumina sintered body (substrate). [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a table showing the conditions and results of the examples and comparative examples. DETAILED DESCRIPTION OF THE INVENTION

[0020] The alumina sintered body member according to the present invention will be described in detail below. The alumina sintered body of the alumina sintered body member according to the present invention contains at least 99.5 wt% aluminum oxide, 100 ppm to 1000 ppm of Mg, 25 ppm to 100 ppm of Na, and 100 ppm to 1000 ppm of Si, and has a density of at least 3.97 g / cm 3 That's all. Furthermore, on any one surface of the alumina sintered body, the average particle size of the alumina particles in a square area (500 × 500 μm) is 2 μm or more and 6 μm or less, the average aspect ratio of the alumina particles is 0.5 or more and 1 or less, the arithmetic mean height Sa of the square area is 0.2 μm or less, and the aspect ratio Str of the surface texture is 0.05 or more and less than 1.

[0021] As described above, the alumina sintered body member according to the present invention is constituted by a characteristic alumina sintered body, and the dielectric loss (tan δ) of this alumina sintered body member at 3 to 7 GHz is 1×10 -5 More than 1×10 -4 The following is less. The alumina sintered body member refers to a member applied to, for example, semiconductor manufacturing equipment, etc., and is formed to a specific shape and dimensions for application. The alumina sintered body also refers to a material or base material that constitutes the alumina sintered body member.

[0022] As described above, the alumina sintered body of the alumina sintered body member according to the present invention contains 99.5 wt % or more of aluminum oxide. Considering that the ceramics used in semiconductor manufacturing equipment, for example, react with plasma gas and the ceramic surface is damaged, it is preferable that the material contains 99.5 wt % or more of highly corrosion-resistant aluminum oxide. If the aluminum oxide is less than 99.5 wt%, there will be a lot of impurities, and the impurities that could not be dissolved in the alumina crystals will segregate at the grain boundaries, which will easily cause local reactions with the plasma gas, leading to the generation of particles.

[0023] The higher the aluminum oxide content of the alumina sintered body, the more suitable it is for an alumina sintered body member. However, the total value of the upper limits of each impurity described below and the unavoidable impurities in the ceramic material may be set to 100 wt%.

[0024] The alumina sintered body also contains 100 ppm or more and 1000 ppm or less of Mg, 25 ppm or more and 100 ppm or less of Na, and 100 ppm or more and 1000 ppm or less of Si.

[0025] As described above, if the amount of Mg contained in the alumina sintered body is less than 100 ppm, sintering will be insufficient and the alumina will not be densified. If the Mg content is more than 1000 ppm, the Mg segregates at the grain boundaries of alumina particles in addition to spinel particles, resulting in an aspect ratio of the alumina particles of less than 0.5. If the aspect ratio of the alumina particles is less than 0.5, it becomes difficult to form a uniform film for the reasons described below.

[0026] When the cross section (surface) of the alumina sintered body is observed, it is found to be composed of alumina particles, grain boundaries existing at the interfaces between these alumina particles, triple junctions where three grain boundaries intersect, and spinel (MgAl2O4) particles. Impurity elements exist as segregated at grain boundaries and triple junctions. However, when aluminum oxide is fired, some of the magnesium is consumed in the production of spinel particles, and the amount of magnesium present as segregated at grain boundaries and triple junctions is smaller than that of other elements present at similar concentrations. At this time, if the Mg concentration is high, more Mg than is consumed in the production of spinel particles will segregate in excess at the grain boundaries of alumina particles or spinel particles.

[0027] That is, in the present invention, it is more preferable to more strictly adjust the amount of Mg to be added so as to minimize the amount of so-called excess Mg in excess of that required for the formation of spinel particles; in other words, to achieve an embodiment in which very little Mg is present at the grain boundaries.

[0028] The alumina sintered body contains 25 ppm or more and 100 ppm or less of Na. Although there is no particular problem in terms of characteristics or quality even if the Na content is less than 25 ppm, a certain amount of Na is always contained in the alumina raw material, and high-purity raw materials with a low Na content are disadvantageous in that they are expensive. On the other hand, when Na is greater than 100 ppm, the dielectric loss is 1×10 -4 This is not desirable as it will be larger.

[0029] The alumina sintered body contains Si in an amount of 100 ppm or more and 1000 ppm or less. Although there is no particular problem in terms of characteristics or quality if the Si content is less than 100 ppm, like Na, a certain amount of Si is always contained in alumina raw materials, and high-purity raw materials with a low Na content are disadvantageous in that they are expensive. On the other hand, if the Si content is more than 1000 ppm, Si segregates at the grain boundaries, causing local reactions with the plasma gas at these locations, which leads to the generation of particles, which is undesirable.

[0030] The density of the alumina sintered body is at least 3.97 g / cm 3 is. A high density allows for the formation of a uniform film with fewer local pores. In the present invention, no upper limit is set, and it can be said that the film can be applied up to the theoretical density. On the other hand, the density is 3.97 g / cm 3 If the thickness is less than 100 nm, the film will be formed along local pores, which may reduce the dry etching resistance.

[0031] In addition, the alumina sintered body has alumina particles in a square area (500×500 μm) on any one surface having an average particle size of 2 μm or more and 6 μm or less and an average aspect ratio of 0.5 or more and 1 or less. The arithmetic mean height Sa of the four-sided area is 0.2 μm or less, and the aspect ratio Str of the surface texture is 0.05 or more and less than 1.

[0032] Here, a (500 x 500 μm) square area on any one surface refers to a (500 x 500 μm) square region at a certain point (one point at the center or several points at equal intervals) on a surface (flat or curved surface) of an alumina sintered body having a predetermined shape (cylinder, flat plate, block, etc.) that is selected and exposed to plasma. One or more of these points can be selected arbitrarily within the surface.

[0033] Furthermore, the surface of the (500 x 500 μm) square area can be observed using various microscopes, visual observation, or image analysis software, etc. However, this does not preclude the use of other methods.

[0034] In the present invention, in a square area (500×500 μm) on any one surface, the alumina particles have an average particle size of 2 μm or more and 6 μm or less, and an average aspect ratio of 0.5 or more and 1 or less.

[0035] As described above, the average particle size of the alumina particles is 2 μm or more and 6 μm or less. If the average grain size is less than 2 μm, triple points consisting of three crystal grains are likely to occur, and as with grain boundaries, impurities are likely to segregate and react with the plasma gas. On the other hand, when the average grain size is larger than 6 μm, the arithmetic mean roughness increases due to the influence of grain shedding that occurs during polishing.

[0036] The average aspect ratio of the alumina particles is 0.5 or more and 1 or less. When forming a film on one surface of an alumina sintered body, film formation is favorable if that surface is an isotropic surface without streaks. Therefore, the aspect ratio of the alumina particles on that surface must be highly isotropic (an aspect ratio close to 1). On the other hand, if the aspect ratio is less than 0.5, the surface will be streaked in one direction, making it difficult to form a uniform film. Furthermore, alumina sintered bodies are sometimes washed with acids such as hydrofluoric acid, and in order to maintain a good surface condition even after acid washing, it is preferable that the aspect ratio is 0.5 or more and 1 or less. Incidentally, in the case of particles with an aspect ratio of less than 0.5, there are many grain boundary intersections per unit area. As a result, it is presumed that if there are many grain boundary intersections, there will be many starting points for corrosion by etching, and it will be difficult to maintain a good surface condition.

[0037] The average particle size or average aspect ratio refers to the average value obtained by randomly selecting a predetermined number (for example, around 200 to 300) of particles observed in a square area (500 × 500 μm) on any one surface, measuring the diameter or aspect ratio of each, and then averaging the measured values. The average particle size or the average aspect ratio can be calculated by observing the surface using various microscopes and then visually observing or using image analysis software.

[0038] The alumina sintered body has an arithmetic mean height Sa of 0.2 μm or less, and an aspect ratio Str of the surface texture of 0.05 or more and less than 1. The arithmetic mean height Sa and the aspect ratio Str of the surface texture are parameters that express the roughness and irregularities on a surface, and they have a particularly large effect on film formation. These values ​​were determined by comprehensively taking into consideration that they can be easily produced as a ceramic material and that the number of these values ​​is the minimum required. That is, although there are many parameters other than Sa and Str that indicate surface texture, the greater the number, the more complex the manufacturing conditions become to keep all the values ​​within a specified range, which is not desirable. In the present invention, it has been discovered that simply controlling these two parameters at a minimum makes it possible to easily achieve both corrosion resistance and low dielectric properties.

[0039] If the arithmetic mean height Sa exceeds 0.2 μm, there is a concern that the unevenness will be too large and it will be difficult to form a uniform film. In the present invention, a small arithmetic mean height Sa does not pose any particular problem in terms of film formation. However, creating such a very flat surface is technically challenging and is not desirable in terms of manufacturing costs. Considering this, it is sufficient for the arithmetic mean height Sa to be 0.01 μm or more.

[0040] The aspect ratio Str of the surface texture is 0.05 or more and less than 1. That is, if the aspect ratio Str of the surface texture is less than 0.05, the surface will have the above-mentioned directional streaks, which is undesirable in that it becomes difficult to form a uniform film. It should be noted that a surface aspect ratio of Str=1 indicates a completely non-directional surface, which is extremely difficult to achieve.

[0041] In the present invention, the surface roughness of the alumina sintered body caused by contact with hydrofluoric acid during acid washing or the like can also be evaluated by the aspect ratio Str of this surface property. That is, if the aspect ratio Str of the surface texture is less than 0.05, the surface may become rough, and the formation of a protective film such as yttria oxide may become non-uniform.

[0042] Furthermore, when the arithmetic mean height Sa and the aspect ratio Str of the surface texture of the alumina sintered body are within the above-mentioned ranges, it is possible to obtain a good flat surface with no undulations or streaky irregularities observed across the entire surface. Such a surface improves the quality of the protective film formed thereon, and the generation of particles can be suppressed.

[0043] The alumina sintered body member (alumina sintered body) has the above-mentioned content of each element, the arithmetic mean height Sa, and the surface texture represented by the aspect ratio Str of the surface texture, and thereby has a dielectric loss (tanδ) of 1×10 at 3 to 7 GHz. -5 More than 1×10 -4 It can be as follows:

[0044] Low dielectric loss alumina has a dielectric loss (tanδ) of 1×10 -4 However, the dielectric loss is generally less than 1×10 in the wide frequency range of 1 to 10 GHz. -4 It is difficult to guarantee the following:

[0045] The inventors of the present invention have found that the reduction of dielectric loss in the vicinity of 5 GHz is influenced to a large extent by the surface properties, and in this invention, they focus on the dielectric loss at 5 GHz and, to a certain extent, reduce the dielectric loss in the range of 3 to 7 GHz, by obtaining a combination of predetermined element concentrations with Sa and Str, in addition to the effect of reducing particle generation. In this way, it is possible to reliably reduce dielectric loss in a narrow frequency band.

[0046] As described above, the alumina sintered body of the alumina sintered body member according to the present invention not only has small surface irregularities, but also has the feature that the irregularities are isotropic, which makes it easier for the protective film formed on the surface to adhere to the surface and enables the film to be formed uniformly. This also makes it possible to prevent the generation of particles originating from pores. Furthermore, since there is little surface roughness even after acid cleaning, acid cleaning can be performed to remove abrasives and processing debris, and then a protective film can be formed uniformly. Therefore, alumina sintered body members with a protective film formed on them can avoid the generation of particles when used in semiconductor manufacturing equipment. Furthermore, such an alumina sintered body can reduce dielectric loss, especially around 5 GHz.

[0047] An alumina sintered body member according to the present invention has a ceramic protective film containing yttrium formed on the surface of a base material made of the above-described alumina sintered body of the present invention. This protective film has a thickness of 1 μm or more and 20 μm or less, a porosity of 0.2% or less, an arithmetic mean height Sa of 0.2 μm or less, and an aspect ratio Str of the surface texture of 0.05 or more and less than 1. Furthermore, this alumina sintered member has a dielectric loss (tan δ) of 1×10 -5 More than 1×10 -4 The following is the result.

[0048] The protective film of the alumina sintered body member of the present invention can be formed on the surface of the alumina sintered body and can further improve corrosion resistance against plasma if it is made of ceramics containing yttrium. Specifically, yttrium oxide can be used. If necessary, various elements (F, Zr, Al, Ti, Si, etc.) may be added to this yttrium oxide.

[0049] Furthermore, if the protective film of the alumina sintered body member of the present invention has a porosity of 0.2 or less, it is possible to prevent particles from being generated from the pores. In the present invention, the smaller the porosity, the better, but it is preferable to set an optimum porosity taking into account the intended use and the manufacturing cost.

[0050] If the thickness of the protective film is less than 1 μm, it is difficult to form the film uniformly. On the other hand, if the thickness of the protective film is greater than 20 μm, it will be necessary to deposit the film multiple times to achieve a uniform film, which will increase manufacturing costs and result in more unevenness than if the entire film thickness were deposited in one go.

[0051] In the alumina sintered body member according to the present invention, the surface properties (Sa, Str) of the alumina sintered body serving as the base material are approximately equivalent to the surface properties of the protective film formed on the surface of the alumina sintered body. This reduces peeling on the surface of the protective film, and the member made of the alumina sintered body also has excellent low dielectric loss characteristics.

[0052] The uniformity of the thickness of the protective film depends on the height of the irregularities on the alumina surface on which the protective film is formed. Specifically, if Sa or Str exceeds the range of the present invention, it is undesirable because there is a concern that the film formed from yttria oxide will not be uniform.

[0053] As described above, the alumina sintered body member of the present invention can be applied to, for example, semiconductor manufacturing equipment, and can efficiently solve the problem of reduced manufacturing yield when processing silicon wafers. [Example]

[0054] The present invention will be specifically described below based on examples, but the present invention is not limited to the examples shown below.

[0055] (Experiment 1) (Preparation of sintered alumina 1 - Common conditions) Alumina powder with a purity of 99.5% or higher was mixed with water as a solvent (equal weight to the alumina powder) and polyvinyl alcohol (2% by weight of alumina) as a binder, spray-granulated, and then sintered at 1600°C in air to obtain a sintered body with a diameter of 500 mm and a thickness of 15 mm. The entire surface of this sintered body was ground using a ceramics grinder.

[0056] (Preparation of alumina sintered body 2 - Adjustment of each condition) The proportion of aluminum oxide was controlled by selecting alumina powder with different aluminum oxide purities, and the density was controlled by changing the firing time. The proportions of Mg, Na, and Si were adjusted by adding appropriate amounts of oxides of each element, and the average particle size was adjusted by changing the particle size of the alumina powder. The average aspect ratio was controlled by adjusting the firing temperature and time. For Sa and Str, the alumina sintered bodies of Examples 1 to 15 and Comparative Examples 1 to 13 in FIG. 1 were obtained by polishing using an abrasive having a particle size of 1 μm or less and adjusting the polishing time between 1 hour and 3 hours to achieve the desired roughness.

[0057] (Rating 1 ~ Density) The density of each alumina sintered body for evaluation was calculated based on JIS R1634 (1998).

[0058] (Evaluation 2 - Average particle size and average aspect ratio) For each alumina sintered body for evaluation, after heat treatment in air at 1550°C for 120 minutes, the grain size was observed in the center of one plane using a scanning electron microscope (SEM), 200 grains observed in one image (500 x 500 μm square) were randomly selected, and the grain size and aspect ratio of each grain were measured, and the average grain size and average aspect ratio were calculated. The field of view was 500x or 1000x.

[0059] (Rating 3 - Surface quality) For each alumina sintered body for evaluation and each alumina sintered body member for evaluation, the same area as in Evaluation 2 was observed using a confocal laser microscope (VK-X1100) manufactured by Keyence Corporation, and the arithmetic mean height Sa and the aspect ratio Str of the surface texture were calculated using the software attached to the device. Sa and Str are calculated based on the International Organization for Standardization ISO25178 (2012).

[0060] (Rating 4 - Dielectric loss) Each alumina sintered body for evaluation was ground to a diameter of 25 mm and a thickness of 10 mm, and then dried in air at 110°C for 1 hour before being measured at a wavelength of 5 GHz using an Agilent 8720ES measuring device at room temperature.

[0061] (Rating 5 - Porosity) The cross section of each alumina sintered body member for evaluation was observed by SEM, and the porosity was determined by measuring the area of ​​pores obtained by cross-sectional electron microscope observation at a magnification of 500 or 1000.

[0062] (Rating 6 - Plasma resistance) Each alumina sintered body or each alumina sintered body member for evaluation was cut to 20 mm so that it could be introduced into a plasma generator, and then placed on a silicon wafer. A mixed gas of argon, carbon tetrafluoride, and oxygen was introduced into the semiconductor manufacturing equipment (etcher), and plasma treatment was carried out for 50 hours at a vacuum of 13 Pa. After the test, particles adhering to the silicon wafer were observed, and if particles of 0.1 μm or larger were found, it was evaluated as not having plasma resistance.

[0063] The conditions and test results for the alumina sintered bodies of Examples 1 to 15 and Comparative Examples 1 to 13 are shown in Table 1 of FIG.

[0064] From the results in Table 1 in FIG. 1, it was confirmed that the alumina sintered bodies within the scope of the present invention were excellent in dielectric loss and plasma resistance.

[0065] (Experiment 2) Next, the alumina sintered bodies for evaluation of Example 1, Comparative Example 1, and Comparative Example 2 were subjected to acid cleaning, and the surface shape and plasma resistance after cleaning were evaluated. The acid cleaning was carried out through the following steps: preliminary water cleaning → immersion in a 9% HF solution for 15 minutes → rinsing with pure water → air drying. The results are shown in Table 2. After washing, the samples were designated Example 1', Comparative Example 1', and Comparative Example 2', respectively. The arithmetic mean height Sa and the aspect ratio Str of the surface texture were measured in the same manner as in Evaluation 3. The plasma resistance was measured in the same manner as in Evaluation 6.

[0066] [Table 2]

[0067] From the results in Table 2, it was confirmed that when the arithmetic mean height Sa and the aspect ratio Str of the surface texture are outside the ranges of the present invention, the surface condition after acid cleaning deteriorates and plasma resistance decreases.

[0068] (Experiment 3) A protective film was formed on the alumina sintered body of Example 1, and alumina sintered body members for evaluation of Examples 16 to 18 and Comparative Examples 14 to 18 were produced by varying the thickness of the protective film. Specifically, an yttrium oxide film was formed by ion plating on one plane of the alumina sintered body of Example 1. At this time, the film thickness and porosity were changed by adjusting the film conditions that would change these, i.e., the film formation rate. For Sa and Str, the specified roughness was achieved by adjusting the polishing time between 1 and 3 hours using an abrasive with a particle size of 1 μm or less, and alumina sintered body members for evaluation were fabricated with different protective film thicknesses, porosities, Sa, and Str, and their plasma resistance was evaluated. The results are shown in Table 3. The thickness of the protective film was determined by observing the cross section of the protective film with an SEM. The porosity and surface texture of the protective film were determined by observing the cross section of the protective film of each alumina sintered body member for evaluation with an SEM and measuring the area of ​​the pores obtained by cross-sectional electron microscopy at a magnification of 500x or 1000x. The arithmetic mean height Sa of the protective film and the aspect ratio Str of the surface texture were determined in the same manner as in Evaluation 3. Plasma resistance was determined in the same manner as in Evaluation 6.

[0069] [Table 3]

[0070] The results in Table 3 show that when the thickness, arithmetic mean height Sa, and aspect ratio Str of the protective film are within the ranges of the present invention, the protective film is properly formed and has sufficient plasma resistance. On the other hand, it was confirmed that when even one of these values ​​is outside the range of the present invention, the plasma resistance deteriorates.

Claims

1. It contains at least 99.5 wt% aluminum oxide, 100 ppm to 1000 ppm of Mg, 25 ppm to 100 ppm of Na, and 100 ppm to 1000 ppm of Si, and has a density of at least 3.97 g / cm 3 The alumina sintered body is On any one surface of the alumina sintered body, the average particle size of the alumina particles in a square area (500 × 500 μm) is 2 μm or more and 6 μm or less, the average aspect ratio of the alumina particles is 0.5 or more and 1 or less, the arithmetic mean height Sa in the square area is 0.2 μm or less, and the aspect ratio Str of the surface texture is 0.05 or more and less than 1, a protective ceramic film containing yttrium is formed on the surface of the alumina sintered body; The alumina sintered member is characterized in that the protective film has a thickness of 1 μm or more and 20 μm or less, a porosity of 0.2% or less, an arithmetic mean height Sa of 0.2 μm or less, and an aspect ratio Str of the surface texture of 0.05 or more and less than 1.

2. The alumina sintered body has a dielectric loss (tan δ) of 1×10 within a range of 3 to 7 GHz. -5 1x10 or more -4 2. The alumina sintered body member according to claim 1, wherein:

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